First Stage Pressure Reducing Valve Having A Tubular Plug, Particularly For Regulators Of Scuba Breathing Apparatus

ABSTRACT

Embodiments of the invention relate to a first stage pressure reducing valve having a tubular plug, particularly for regulators of scuba breathing apparatus. According to embodiments of the invention, at least a portion of the outer surface of the valve has fins for heat exchange with the outside environment, designed to prevent or reduce the formation of ice caused by the temperature drop generated by gas expansion inside the valve.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation of co-pending U.S. patentapplication Ser. No. 10/448,072, filed May 30, 2003, which claims thebenefit of Italian Application No. SV2002A000026, filed May 30, 2002,the entire teachings and disclosure of which are incorporated herein byreference thereto.

FIELD OF THE INVENTION

The invention relates to a first stage pressure reducing valve having atubular plug, particularly for regulators of scuba breathing apparatus.

BACKGROUND OF THE INVENTION

Various devices are known that can accomplish this function. Thisinvention particularly addresses a first stage of pressure reduction inair supplied by a pressure source, generally one or more bottles. Thensaid lower pressure air is supplied to a second stage, which furtherreduces its pressure and adapts it for breathing purposes. This type offirst stage valves generally has two axially adjacent chambers,separated by a partition wall, one having the function of automaticallycompensating outlet pressure with reference to ambient pressure andcommunicating with the outside environment through one or more holes orapertures in the peripheral wall, and the other, the so-called pressurechamber, communicating with a compressed air source, whereas a tubularplug passes slidably and tightly through the partition, which plug isopen at both ends, one end being in the compensation chamber and theother end being in the pressure chamber, the end situated in thecompensation chamber having a widened piston-like head which is arrangedto slide in a tight manner in the compensation chamber, and to separatethe latter from an outlet chamber situated on the piston side oppositeto the partition wall, and in which the respective end of the tubularplug opens, creating a passage for communication with the pressurechamber, a helical pressure spring, particularly coaxial to the tubularplug, being interposed between said piston-like head of the tubular plugand the partition wall, which helical spring pushes the plug toward theopening position, while the same plug is pushed toward the closingposition by the air pressure in the outlet chamber.

This type of valves, particularly in very low temperature water diving,and especially in fresh water, may be exposed to a potentially seriousdrawback, that may even be dangerous for the diver's safety. The rapidexpansion of the gas supplied by the high pressure source, occurring inthe outlet chamber, is an adiabatic process which causes a considerabletemperature drop in the surrounding environment, due to energyabsorption by the gas. The parts that are mostly affected by thistemperature drop are the tubular plug body, which forms the passage forcommunication between the pressure chamber and the outlet chamber, theenlarged plug head and the boundary wall of the outlet chamber and thecompensation chamber. In this connection, it shall be noted that theboundary wall of these two chambers is partly shared thereby, since theoutlet chamber is formed by the sliding motion of the enlarged head,caused by progressive gas expansion. The transfer of cold to the outsidemay lead to a progressive formation of ice upon the outer surface of theboundary wall of the outlet chamber and of the compensation chamber,further facilitated by the fact that this wall is generally made ofmetal having a high thermal conductivity and that, as is known, waterhas a high heat capacity. Ice formation may extend by progressiveaccumulation to the compensation hole area, resulting in a reduction ofhole diameters or even in hole obstructions, whereby the communicationof the compensation chamber with the outside environment is reduced oreven prevented. Also, since water inside the compensation chamber issubstantially stationary and there is a very small exchange with theoutside environment due to the poor pumping effect generated by thereciprocating motion of the enlarged plug head, ice may even formbetween the turns of the spring thereby preventing the proper slidingmotion of the tubular plug. Ice formation in the compensation chamberand/or on the outer surface of the outlet chamber and/or thecompensation chamber may have very serious consequences, includingpermanent valve opening, and fast bottle depletion.

Various arrangements have been proposed to obviate this seriousdrawback, all being based on the interposition of two or more thermalinsulating members between the various metal surfaces in contact witheach other and/or with cold water and/or with outside water and/or withthe water of the compensation chamber. One of these arrangements alsoconsists in coating the helical spring with a heat insulating material.These arrangements are all designed to generate a discontinuity in coldtransfer from the air in the outlet chamber to the various metal partsin contact with it and with each other, and from the latter to water, sothat icing may be reduced. Nevertheless, these well known arrangementsinvolve a more difficult manufacture of the valve, and an increase ofthe cost thereof. Moreover, certain parts, particularly the tubular plugbody, cannot be heat insulated, whereby cold is still transmitted,though to a reduced extent, from the inside to the outside.

BRIEF SUMMARY OF THE INVENTION

Therefore, an embodiment of this invention has the object of obviatingthe above drawbacks and providing, by simple and inexpensive means, afirst stage pressure reducing valve having a tubular plug like the onedescribed hereinbefore, which ensures proper and full operation in anysituation whatsoever, particularly in very low temperature water diving,with no or very little ice formation, anyway insignificant for propervalve operation.

An embodiment of the invention achieves the above purposes by providinga first stage pressure reducing valve having a tubular plug like the onedescribed hereinbefore, wherein at least a portion of the outer surfaceof the valve has fins for heat exchange with the outside environment.First, it shall be noted that embodiments of the invention are based ona principle which is the inverse of the one normally used in prior artvalves to prevent the formation of ice, i.e. valve insulation. Sincediving water always has a temperature above the icing point, thearrangement was found to alter the heat exchange between the valve bodyand the outside environment, so that a reduction in icing of theexternal water is achieved. This is counter-intuitive as typically, theaddition of fins would lead one to believe that more heat energy wouldbe removed from the local water environment causing icing to increase asopposed to reduce.

Here, fins are provided on the outer surface of the union, upstream froma piston-like plug which opens and closes the inlet pipe communicatingwith said union. Hence, according to this arrangement, fins are providedin the high pressure area of the reducing valve, which is also adiaphragm valve at the second stage.

Apart from the fact that the most significant pressure reduction, hencethe adiabatic expansion and cooling resulting therefrom, occur in thefirst stage reduction valve, whereby the proposed arrangement does notsolve the icing problem at the first reduction stage, fins are providedin the high pressure area, where cooling is less significant.

Another important consideration to be made is that the malfunctioning ofreducing valves, particularly of first stage reducing valves, and moreparticularly to those having a tubular plug (as the one describedabove), is mainly caused by water freezing in the compensation chamberand between the spring turns, acting on the tubular plug in the openingdirection. In fact, icing between the spring turns, prevents the springfrom operating properly, due to the reduction of its spring modulus inproportion to the turns blocked by ice, and has detrimental effects onthe equilibrium of forces, which is a basic condition for propermetering of air supplied to the outlet chamber of the valve.

Due to the above, the invention is aimed at providing heat exchange finsin the low pressure area of the chamber/s of the reducing valve.

Particular advantages are obtained from the provision of fins for heatexchange with the surrounding environment on at least a portion of theouter boundary wall of the outlet chamber and/or the compensationchamber. In fact these chambers were found to the mostly exposed toadiabatic expansion cooling, therefore to icing. Further, heat exchangewith the outside environment is allowed in the spring containingchamber, thereby effectively obviating any malfunctioning due to iceformation between the spring turns or around the spring.

In accordance with a first embodiment, which will be described ingreater detail in the description of the drawings, said fins may be madeof one piece with the outer boundary wall of the outlet chamber and/orthe compensation chamber.

Said outer wall may have a substantially cylindrical shape, andcommunicate, at one of its axial ends, with an axial terminal forconnection to an air outlet pipe, particularly used to supply air to thesecond stage which further reduces pressure to a breathable level. Inthis connection, it shall be noted that most of the pressure reducingfunction is accomplished by the first stage, e.g. from 300 to 30atmospheres, and it is also for this reason that the first stage isparticularly exposed to cooling.

Fins may extend continuously along the whole outer surface of theboundary wall of the outlet chamber and/or the compensation chamber. Inaccordance with a preferred embodiment, the latter may be provided inthe form of individual annular flanges, coaxial to said chamber/s andaxially spaced to a predetermined extent. However, the word fins as usedin this description shall be generally intended as indicative of heatexchange surfaces or projections of any shape, anyway used to extend theboundary wall of the outlet chamber and the compensation chamber toincrease the heat exchange with the outside environment. The abovepreferred embodiment of fin construction has construction simplicityadvantages, due to the facts that fins may be obtained by forming simpleaxially spaced annular grooves, which are strong and even less annoyingand dangerous for the user as compared to other different arrangements.An additional important function of said fins consists in preventing,even by mechanical means, the formation of ice caused by the transferand/or progressive accumulation of the ice mass as compared with theresults that would be obtained with a smooth wall.

The holes whereby the communication chamber communicates with theoutside environment may be arranged along a peripheral annular band ofthe compensation chamber boundary wall.

Fins may also extend axially up to the hole area and end at the edge ofsaid holes turned towards the connection terminal.

In a second embodiment, which will be described in greater detail in thedescription of the drawings, the fins designed for heat exchange withthe outside environment may be at least partly added thereto, andconsist of a separate finned bush-like element which is applied to theoutside of the boundary wall of the outlet chamber and/or thecompensation chamber, and is made of a highly heat conductive material,particularly of a metal material, such as brass or the like. This secondarrangement has the advantage that the outside diameter of the addedelement may be much longer than in the one-piece solution, thanks to thefact that it does not depend on the processing diameter of the cup- orhood-like element which forms the outside boundary wall of the outletchamber and the compensation chamber. Obviously, the applied elementmust also have excellent heat conductivity properties. An additionaladvantage of the above second embodiment may be the possibility ofmodifying existing finless reducing valves by laying an appropriatefinned member over them.

This finned element may be held in position by screwing or force fittingit or the like. Alternatively thereto or in combination therewith, thelatter may be held axially between the connection terminal and anannular shoulder provided along the outer surface of the boundary wallof the outlet chamber and/or the compensation chamber.

Particularly, this outer wall may be formed in such a manner that ittapers in annular steps toward the end for connection to the connectionterminal whereas the applied finned element may have a correspondinginside shade which tapers in steps toward the connection terminal.

The applied finned element may have, at its end turned towards theconnection terminal, an annular inside shoulder and may be held inposition by the clamping action of the connection terminal against theopposite face of a corresponding annular step which is provided alongthe outer boundary surface of the outlet chamber and the compensationchamber.

With reference to both the embodiments prescribed above, the fin that isprovided in the hole area may have at least one additional annular findisposed over the holes at a certain distance therefrom, which leaves acommunication passage from the compensation chamber to the outsideenvironment, whose axis is oriented transverse, particularlyperpendicular, to the hole axis.

By this arrangement, a sort of partition or screen is formed for holeprotection, which mechanically prevents any formation of ice “bridges”over the holes. Even when one or more of these bridges are formed, theabove mentioned supplementary fin anyway leaves a free passage for waterbetween two adjacent bridges.

According to a highly advantageous improvement, at least a portion ofthe boundary wall of the connection terminal may be also provided withfins for heat exchange with the outside environment, since theconnection terminal is in heat exchanging contact with the boundary wallof the outlet chamber and/or the compensation chamber and is a cold airtransit zone, hence it is itself exposed to cooling. These fins may beat least partly made of one piece with the connection terminal body, ormay be at least partly added thereto, and made in a manner similar to,the fins provided on the outer boundary wall of the outlet chamber andthe compensation chamber.

The advantages of embodiments of the invention are apparent from theabove disclosure, and substantially consist in allowing, by very simpleand inexpensive means, an improved interaction with the surroundingwater to reduce icing by extending the surface in contact with water.The whole is obtained by implementing an arrangement having a verysimple and inexpensive construction. Further, heat exchange is furtherfacilitated in the valve parts that are more exposed to cooling or tomalfunctioning due to icing, and that strongly affect the pressurereducing valve operation.

Further characteristics and improvements will form the subject of thedependent claims.

Other aspects, objectives and advantages of the invention will becomemore apparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thespecification illustrate several aspects of the present invention and,together with the description, serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a longitudinal section view of a first stage pressure reducingvalve having a tubular plug according to the prior art.

FIG. 2 is a longitudinal section view of a first stage pressure reducingvalve having a tubular plug according to the invention.

FIG. 3 is a longitudinal section view of a second embodiment of a firststage pressure reducing valve having a tubular plug according to theinvention.

FIG. 4 is a longitudinal sectional view of a first embodiment of a firststage pressure reducing valve having a tubular plug according to theinvention, in which the upper axial half shows the prior art and theother axial half shows the invention, with reference to the axis of thetubular plug.

FIG. 5 is a longitudinal sectional view of a second embodiment of afirst stage pressure reducing valve having a tubular plug according tothe invention, in which the upper axial half shows the prior art and theother axial half shows the invention, still with reference to the axisof the tubular plug.

While the invention will be described in connection with certainpreferred embodiments, there is no intent to limit it to thoseembodiments. On the contrary, the intent is to cover all alternatives,modifications and equivalents as included within the spirit and scope ofthe invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The two embodiments of first stage pressure reducing valves having atubular plug, as shown in the drawings and designed according to theinvention provide a reduced outlet pressure which is automaticallycontrolled relative to ambient pressure and are pressure reducing valvesfor the first reduction stage of regulators for scuba breathingapparatus.

With reference to FIGS. 1-5, this type of pressure reducing valveincludes a body 1 divided by a partition wall 2 into two separate andaxially adjacent chambers 3 and 4. The chamber 3 is the so-calledcompensation chamber and communicates through one or more lateral holes5 with the outside environment. The chamber 4 is the so-called pressurechamber and is connected through a lateral hole 7 and a fitting 6 in awell-known manner to a compressed gas (e.g. oxygen or air) bottle.

A tubular plug 8, whose ends are both open, passes in an axially andtightly slidable manner through the partition wall 2. The tubular plug 8has an enlarged head 9 at the end projecting into the compensationchamber 3, which is made in the form of a piston and is tightly slidablein the body 1 of the valve, thereby separating the compensation chamber3 from an outlet chamber 14, in which the corresponding end of thetubular plug 8 opens, and which is connected through a hole 10 to anaxial terminal 13, whereto a pipe 12 is connected by means of a fitting11, which supplies air to a second stage (not shown). A helicalcompensation spring 15 is provided between the piston-like head 9 of thetubular plug 8 and the partition wall 2. The other end 108 of thetubular plug 8, that projects into the pressure chamber 4, cooperates bythe circular edge of its opening with a pad 16 which acts as the valveseat. A helical pressure spring 17 is provided in the pressure chamber 4between the partition wall 2 and the pad 16.

The operation of such type of valves is well-known. Compressed airpasses through the hole 7 and penetrates the pressure chamber 4,expanding through the open end 108 of the tubular plug 8, into theoutlet chamber 14. Air pressure, which acts on the enlarged head 9 ofthe tubular plug 8, causes the plug 8 to slide until its end 108contacts the pad 16 thereby preventing any further ingress of air intothe outlet chamber 14. The tubular plug 8 slides against the action ofthe helical spring 15, which brings the tubular plug 8 back to theopening position when the outlet chamber 14 is emptied, for instanceupon one or more breathing actions. The tubular plug 8 also slidesagainst the pressure of the water wherein the diver dives which, bypenetrating the compensation chamber 3 through the holes 5,counterbalances the pressure in the outlet chamber 14 relative toambient pressure. This arrangement allows the diver to breathe air at apressure that increases with the increase of the diving depth, hence ofoutlet pressure.

Referring to the upper axial half of FIGS. 4 and 5, and particularly tothe axis of the tubular plug 8, a possible behavior of a prior art valveduring diving, particularly in very low temperature water, next to thefreezing point, is shown. The rapid expansion of air in the outletchamber 14, which is required to reduce pressure enough to allow it tobe appropriately supplied to the second stage, causes a cooling thereofand, as a result, of all metal parts wherewith it is in contact,particularly the boundary wall 114 of the outlet chamber 14 and thecompensation chambers 3. This unavoidable fact may lead to the formationof an ice layer 18 outside the wall 114 and possibly, as shown in thefigures, on the outer surface of the axial air outlet terminal 13. Theice layer 18 may progressively extend to reduce the diameter or evenobstruct one or more of the holes 5 for communication of thecompensation chamber 3 with the outside environment, thereby reducing oractually preventing its proper operation. Moreover, since there is apoor water exchange between the inside of the compensation chamber 3 andthe outside, ice 18 may be formed even inside it, and particularlybetween the adjacent turns of the helical spring 15, thereby hinderingor preventing the tubular plug 8 from sliding in the closing direction.The consequences thereof may be easily deducted and consist in anexcessive expansion of air in the outlet chamber 14 when holes 5 areobstructed, since the air expansion action is only contrasted by thehelical spring 15 and not by water outside pressure. Further, if theelastic movement of the spring 17 is blocked by ice, air expansionwithin the chamber 14 occurs to a reduced extent or does not occur atall. This may result in an improper air supply to the second stageand/or in a fast depletion of the bottle with easily deductibleconsequences.

In order to obviate such serious drawback a first embodiment of theinvention, as shown in FIG. 2 and in the lower axial half of FIG. 4provides that the outer boundary wall 114 of the outlet chamber 14 andthe compensation chamber 3 has a plurality of fins 19 which form a finarrangement designed for modified heat exchange with the outsideenvironment 19, i.e. with the water wherein the valve is submersed,which water, always above 0° C., keeps the various exposed parts to atemperature above icing, thanks to the modification of the heat transfersurface provided by the fins 19. This modification causes the fins todraw less heat from localized water and to draw heat from a largervolume of water. This hinders or prevents icing by actually reducing theamount of heat drawn from individual quantities of water, but by drawingheat from a larger volume of water. In such first embodiment, the heattransfer fins are made of one piece with the outer wall 114, whereas thefins 19 extend continuously along the whole outer surface of the wall114 which has a substantially cylindrical shape and is made in the formof a hood or a cup. The fins 19 are made in the form of individualannular flanges 19, which are coaxial to the outlet chamber and thecompensation chamber 3 and are axially spaced to a predetermined extent.In both illustrated embodiments, the axial connection terminal 13 isalso provided with fins for heat exchange with the outside which areradial annular fins 113 like those provided on the outer wall of theoutlet chamber 14.

Referring now to FIGS. 3 and 5, a second embodiment of the invention isshown, in which the fins are provided in a separate finned element 20which has the form of a bush to be laid over the outer boundary wall 114of the outlet chamber 14 and the compensation chamber 3. Nevertheless,the heat exchange fins 19 are made as provided in the previousembodiment. In this case, the outer wall 114 tapers in annular stepstoward the end for connection to the connection terminal 13 whereas theapplied finned element 20 may have a corresponding inside shape whichtapers in steps toward the connection terminal 13. This finned element20 has an inner annular shoulder 120, at its end turned toward theconnection terminal 13, and is held axially in position thanks to thefact that the connection terminal 13 is clamped against the oppositeface of a corresponding annular step 214 which is provided along theouter surface of the wall 114.

In accordance with an advantageous improvement, in both illustratedembodiments, the first fin 19′ with reference to the air outletdirection, is provided next to the hole side 5 turned toward theconnection terminal 13 for communication of the compensation chamber 3with the outside environment, which holes 5 are provided along anannular peripheral band of the boundary wall 114 of said chamber 3. Inorder to further contrast the formation of ice 18 in the hole area 5,said first fin 19′ has an additional annular fin 119′ and lays over theholes 5 at a certain distance therefrom, thereby leaving a communicationpassage from the compensation chamber 3 to the outside environment. Asis shown in the figures, the latter annular fin 119′ has the function ofcontrasting, even mechanically, the formation of ice 18 in the hole area5, and even when bridges 118 or ice 18 are formed in this area, said fin119′ still allows communication between the compensation chamber 3 andthe outside environment.

It shall be noted that the step-like outer tapers of the valve body andinner tapers of the ring of heat exchange fins, have the additionaladvantage of increasing the contact surface between said heat exchangering and the reducing valve, thereby improving the heat exchange effectsbetween said two parts.

Obviously, the invention is not limited to the two embodiments describedand illustrated herein, but may be greatly varied, without departurefrom the guiding principle disclosed above and claimed below.

All references, including publications, patent applications, and patentscited herein are hereby incorporated by reference to the same extent asif each reference were individually and specifically indicated to beincorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) is to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A first stage pressure reducing valve for regulators of underwaterscuba breathing apparatus comprising: a valve member; a valve bodydefining a cavity in which the valve member is slidably received, thevalve member separating the cavity into a high pressure chamber and anoutlet chamber, the valve member slidable between an open positionwherein the high pressure chamber fluidly communicates with the outletchamber and a closed position wherein the high pressure chamber isprevented from fluidly communicating with the outlet chamber, the valvemember and valve body further defining a pressure compensation chambertherebetween, the pressure compensation cavity including a hole fluidlycommunicating the pressure compensation cavity with the ambient watersurrounding the valve; a biasing member biasing the valve member towardsthe outlet chamber; and a plurality of fins positioned proximate thehole preventing ice from forming and obstructing the hole.
 2. The firststage pressure reducing valve of claim 1, wherein the outlet chamber isa low pressure area of the valve body and the heat transfer fins areprovided in the low pressure area of the valve body.
 3. The first stagepressure reducing valve of claim 1, wherein the heat transfer fins areintegrally formed with the valve body.
 4. The first stage pressurereducing valve of claim 1, wherein the heat transfer fins are a separatecomponent piece coupled to the valve body.
 5. The first stage pressurereducing valve of claim 1, wherein the valve body includes a partitionwall separating the high pressure chamber from the compensation chamberand the valve member is in the form of a tubular plug slidably passingthrough the partition wall having one end in the high pressure chamberand the other end being a piston-like head in the compensation chamber,the piston-like head separating the compensation chamber from the outletchamber with the outlet chamber on the side of the piston-like headopposite the partition wall.
 6. The first stage pressure reducing valveof claim 5, wherein the biasing member is positioned within the pressurecompensation cavity.
 7. The first stage pressure reducing valve of claim1, wherein the plurality of fins includes at least one annular findisposed over the hole at a certain distance therefrom, which leaves acommunication passage from the compensation chamber to the ambientsurroundings whose axis is oriented transverse to the hole axis.
 8. Thefirst stage pressure reducing valve of claim 5, further including aconnection terminal coupled to the valve body communicating with theoutlet chamber, the coupling terminal providing a connector forconnecting the valve body to an air outlet pipe and wherein theplurality of fins are formed as a separate finned element secured to thevalve body by the coupling terminal.
 9. The first stage pressurereducing valve of claim 8, wherein a wall forming an outer surface ofthe valve body and forming the outlet chamber and the compensationchamber tapers in annular steps that get larger in a direction extendingaway from the connection terminal and toward the compensation chamberand the element has a corresponding inside shape which tapers incorresponding steps increasing the contact surface between the finnedelement and the outer surface of the wall.
 10. The first stage pressurereducing valve of claim 9, wherein the finned element is clamped betweenradially outward projecting portions of the steps of the wall and theconnection terminal.
 11. The first stage pressure reducing valve ofclaim 1, wherein the pressure compensation cavity includes a pluralityof holes fluidly communicating the pressure compensation cavity with theambient surroundings of the valve and the a plurality of fins arepositioned proximate the holes preventing ice from obstructing the hole.12. The first stage pressure reducing valve of claim 1, wherein one ofthe plurality of fins axially ends at an edge of the hole.
 13. The firststage pressure reducing valve of claim 1, wherein the plurality of finsare annular fins that entirely surround the outlet chamber.
 14. A firststage pressure reducing valve for regulators of underwater scubabreathing apparatus comprising: a valve member; a valve body defining acavity in which the valve member is slidably received, the valve memberseparating the cavity into a high pressure chamber and an outlet chambera high pressure chamber, the valve member slidable between an openposition wherein the high pressure chamber fluidly communicates with theoutlet chamber and a closed position wherein the high pressure chamberis prevented from fluidly communicating with the outlet chamber, thevalve member and valve body further defining a pressure compensationcavity therebetween, the pressure compensation cavity including a holefluidly communicating the pressure compensation cavity with the ambientsurroundings of the valve; a biasing member biasing the valve membertowards the outlet chamber; and means for retarding ice formation on anouter surface of the valve body to prevent ice from obstructing thehole.
 15. The first stage pressure reducing valve of claim 14, whereinthe retarding means are integrally formed in a boundary wall of thevalve body.
 16. The first stage pressure reducing valve of claim 14,wherein the retarding means are formed as a separate retarding elementthat is independently couplable to a boundary wall of the valve body.17. The first stage pressure reducing valve of claim 14, wherein theretarding means only partly angularly surrounds the outlet chamber. 18.A method of reducing ice formation of ambient water surrounding a firststage pressure regulator to prevent obstruction of fluid communicationbetween the ambient surroundings of first stage pressure reducing valveand a pressure compensation cavity, the pressure compensation cavitybeing separated from an outlet chamber of the valve body by a valvemember that is biased towards the outlet chamber by a biasing means, thebiasing of the valve member towards the outlet chamber is compensated bychanges in pressure of the ambient acting on the valve member, furtherwherein a temperature gradient across a boundary wall separating theoutlet chamber and the ambient is such that the outlet chamber is at alower temperature than the ambient, the method comprising the step of:reducing the amount of heat transferred from localized portions of theambient water by drawing heat from a larger amount of ambient water. 19.The method of claim 18, further including the step of mounting a finnedelement to the boundary wall of the valve body.